There is a lot of fear being spread around the world about global warming and catastrophic climate change. Some fools are even promoting a series of music events on all seven continents to promote their message that we must act now. They say the crises is upon us and the need is urgent to stop global warming.
Unfortunately these people always seem to ignore science, history, and even simple common sense. They rely on their feelings rather than reason and logical thought. Read this article about human evolution. Modern humans evolved, spread and thrived through ice ages, and every kind of natural disaster and climate changes, more severe than we are experiencing now. This is not mere speculation, but fact based on the study of written history and archaeology, (ancient Egyptians, Mayans, Aztecs, etc.). That is not all.
Now, as the following article explains, DNA evidence in human genes is showing how remarkably adaptable human beings are to changes in climate, diet, exposure to diseases, and probably everything else in our environment. Are we being unnecessarily frightened by current weather events and global warming? Only you can answer that question for yourself. Maybe it is just human nature to be afraid, to be cautious. Maybe that helps our survival. My advice is to not believe everything you are told or hear.
Humans Have Spread Globally, and Evolved Locally
By NICHOLAS WADE
Published: June 26, 2007
Historians often assume that they need pay no attention to human evolution because the process ground to a halt in the distant past. That assumption is looking less and less secure in light of new findings based on decoding human DNA.
People have continued to evolve since leaving the ancestral homeland in northeastern Africa some 50,000 years ago, both through the random process known as genetic drift and through natural selection. The genome bears many fingerprints in places where natural selection has recently remolded the human clay, researchers have found, as people in the various continents adapted to new diseases, climates, diets and, perhaps, behavioral demands.
A striking feature of many of these changes is that they are local. The genes under selective pressure found in one continent-based population or race are mostly different from those that occur in the others. These genes so far make up a small fraction of all human genes.
A notable instance of recent natural selection is the emergence of lactose tolerance — the ability to digest lactose in adulthood — among the cattle-herding people of northern Europe some 5,000 years ago. Lactase, the enzyme that digests the principal sugar of milk, is usually switched off after weaning. But because of the great nutritional benefit for cattle herders of being able to digest lactose in adulthood, a genetic change that keeps the lactase gene switched on spread through the population.
Lactose tolerance is not confined to Europeans. Last year, Sarah Tishkoff of the University of Maryland and colleagues tested 43 ethnic groups in East Africa and found three separate mutations, all different from the European one, that keep the lactase gene switched on in adulthood. One of the mutations, found in peoples of Kenya and Tanzania, may have arisen as recently as 3,000 years ago.
That lactose tolerance has evolved independently four times is an instance of convergent evolution. Natural selection has used the different mutations available in European and East African populations to make each develop lactose tolerance. In Africa, those who carried the mutation were able to leave 10 times more progeny, creating a strong selective advantage.
Researchers studying other single genes have found evidence for recent evolutionary change in the genes that mediate conditions like skin color, resistance to malaria and salt retention.
The most striking instances of recent human evolution have emerged from a new kind of study, one in which the genome is scanned for evidence of selective pressures by looking at a few hundred thousand specific sites where variation is common.
Last year Benjamin Voight, Jonathan Pritchard and colleagues at the University of Chicago searched for genes under natural selection in Africans, Europeans and East Asians. In each race, some 200 genes showed signals of selection, but without much overlap, suggesting that the populations on each continent were adapting to local challenges.
Another study, by Scott Williamson of Cornell University and colleagues, published in PLoS Genetics this month, found 100 genes under selection in Chinese, African-Americans and European-Americans.
In most cases, the source of selective pressure is unknown. But many genes associated with resistance to disease emerge from the scans, confirming that disease is a powerful selective force. Another category of genes under selective pressure covers those involved in metabolism, suggesting that people were responding to changes in diet, perhaps associated with the switch from hunting and gathering to agriculture.
(the article is continued at the original source)